1. Field of the Invention
The present invention relates to a metal gasket, and more particularly, relates to an improvement of a metal gasket which is preferably used for a joining seal between a cylinder block and an exhaust manifold of an internal combustion engine.
2. Description of the Related Art
The gasket used in an internal combustion engine or the like has an opening for a cylinder which needs sealing and a bolt hole for fastening the gasket and the companion flange with a bolt for fastening.
Normally, the diameter of the bolt hole for attachment which is provided in the metal gasket is made larger than the diameter of the bolt to be used generally both for making the attachment of the gasket easy, and for absorbing the positional declination of the hole for attachment which is provided in the companion member.
In the case where the companion surface to which the metal gasket is attached is horizontal or has an angle larger than a right angle relative to the ground, it does not occur for the mounted metal gasket to move or to drop off because of vibration or the like, even if, for example, the mounting is performed by passing the bolt hole of the metal gasket onto the stud bolt on the attaching companion surface side in advance.
However, in the case where the attaching surface has an angle smaller than the verticality (is included to the ground surface side) or in the case where vibration is applied after the mounting, the metal gasket mounted on the bolt may move, or in some cases, drop off.
Especially, in the case of a gasket for the exhaust manifold of a V-type engine or the like, the attaching surface is inclined to the ground surface side, and therefore, it is necessary to incline the engine so that the attaching surface has an angle larger than at least the right angle or more for the mounting of the gasket.
Furthermore, in the case where the attaching surface is inclined to the ground surface side from the rectangular direction of the ground surface or in the case where the attaching surface cannot be inclined because of the peripheral equipment, the mounting of the metal gasket becomes very difficult.
As one for solving the problem, Japanese Patent Application Laid-Open No. 8-49597 proposes a metal gasket which is composed such that at the base plate part near the hole for attachment of the metal base plate, an engaging part projecting to the hole for attachment is provided by cutting work or the like.
According to the construction of this metal gasket, at the time of insertion of a shaft member into the hole for attachment provided in the metal gasket, the engaging part which has been struck against the shaft member is elastically bent and allows the insertion of the shaft member, and the metal gasket can firmly be held at the inserting position by the pressing action to the shaft member by the impact resilience force to be produced at that moment.
However, the gasket with the construction can easily be removed if the companion shaft member has a smooth peripheral surface like a pin, but in the case where the shaft member is a bolt for fastening, the bolt engaging part is caught by the screw part of the bolt and acts as a stopper, and therefore, it cannot easily be removed.
It is a main object of the present invention to provide a metal gasket wherein even if the shaft part is any one of a pin or a bolt, attaching and removing can easily be performed, and dropping off can be prevented.
In order to overcome the problems, the invention according to a first aspect is a metal gasket comprising one or a plurality of laminated metal base plates, wherein at the base plate part near the bolt hole for attachment which is provided in the metal base plate, a bolt engaging piece projects so that the diameter of the bolt hole is smaller than the diameter of the bolt for fastening, and an assistant piece used for the handling of separating the bolt engaging piece from the bolt is formed integrally with the bolt engaging piece.
Furthermore, the invention according to a second aspect is the metal gasket according to the first aspect, wherein the bolt engaging piece and the assistant piece for handling are formed by cutting work of the metal base plate.